1. Field of the Invention
The present invention is directed to a method and apparatus corresponding to an insert for an article of footwear with improved elastically deformable elements and arrangements therefor which permit optimization of the biomechanics of a user's foot.
2. Discussion of the Background
Barrel shaped elastically deformable elements are taught in the U.S. Pat. No. 5,092,060 issued to Frachey et al and U.S. Pat. No. 5,396,896 issued to Frachey et al, the subject matter of which is hereby expressly incorporated by reference into this application and which is illustrated in FIGS. 179-182. Frachey et al '060 and '896 teach an article of footwear comprising a vamp A at a lower support part 1 which comprises a sole 2 a wedge 3, a mounting insole 5, and a further insole 6. Elastically deformable elements 14 of Frachey et al '060 contained inside an insert 13, are arranged in seat 16 formed in wedge 3. The deformable elements 14 are formed by molding a synthetic high elasticity material and are substantially barrel shaped, with their major cross-sections being substantially in the central region 20 in which said elements are joined together by an integral bridging portion 28. Deformable elements 14 are arranged in an insert 13 made of thermoplastic material enclosed in an airtight casing 15 which is constructed of plastic material such as polyurethane or similar material. The air inside casing 15 has a pressure of less than or equal to atmospheric pressure.
With reference to FIGS. 179-182 of the present application, the article of footwear of Frachey et al '060 comprises a vamp A and a lower support part 1 comprising a sole 2, for example of synthetic rubber, to which a wedge 3, for example of thermoplastic polyurethane, is fixed in a known manner. The wedge comprises a recess 4, bounded by a raised edge 10, carrying a mounting insole 5, for example a cork, on which there is positioned a further insole 6, for example of fabric (not shown in FIG. 181). The sole 2, constructed advantageously of rubber, comprises the usual notches 7 and incisions or recessed portions 8 in its lower surface. It also comprises a front raised edge 11, and a lateral edge 12 which extends along the entire remaining perimeter of the sole.
According to this conventional article of footwear, in the lower part of the article of footwear there is arranged an insert 13 comprising elastically deformable elements 14 made of thermoplastic material enclosed in an air-tight casing 15 constructed of plastic material such as polyurethane or a similar material. In casing 15 there is present air that has a pressure less than or equal to atmospheric pressure. In this example, the insert 13 is positioned in seats 16 and 17 provided in the wedge 3 and in the insole 5 respectively, said seats being superposed. Alternatively, seat 17 can be omitted with insert 13 located only in seat 16 of wedge 3, so that the insole 5 is superimposed and covers seat 16.
More specifically, the elements 14 of the insert 13 are formed by molding any synthetic high-elasticity material and are substantially barrel-shaped, i.e., they are tapered at their opposing free ends 18 and 19 and have their major cross-section substantially in the central region 20 in which said elements are joined together by an integral bridging portion 20A. The barrel shaped elements are barrel shaped in the sense that all vertical cross sections taken along the vertical axis thereof are barrel shaped. Due to manufacturing requirements of insert 13, free ends, 18, 19 of barrel-shaped elements 14 are fastened to casing 15. This is actually the preferred embodiment of insert 13, wherein in a first phase, elements 14 are obtained by means of molding; subsequently they are encased inside thermo-soldering plastic sheets which constitute casing 15; the elements 14 are encased by sheets when they are at a relatively high temperature so that a welding of free ends 18, 19 of elements 14 with the sheets occurs. The connection between casing 15 and the barrel-shaped elements has the advantage of anchoring said elements inside said casing, thereby preventing the casing and barrel-shaped elements from moving during use of the article of footwear according to the invention and so contributing together with the mutual connection of the barrel-shaped elements 14 to desirable multidirectional stability and flexibility of the resulting article of footwear. This affords greater stability for insert 13 within the article of footwear, and permits better performance of the function for which it is intended, which functions will be further defined below.
The shape of elements 14, as shown and described by way of example, allows considerable absorption of the stresses caused by the user's foot as he moves, and at the same time allows a large part of the absorbed energy to be retransmitted rapidly but gradually to the foot. In order to secure the insert 13 within the seats 16 and 17, the insole 6 comprises on that face 21, facing the insole 5, a projection 22 of a shape corresponding to said seats and arranged to cooperate with them and with the insert 13. In the alternative embodiment recited above, the projection 22 can be omitted. The casing 15 of insert 13 comprises a flange 23 which, when the insert 13 has been positioned in the lower part 1 of the article of footwear, rests on a step 24 provided between the insole 5 and an inner surface 25 of the wedge 3. In the alternative, where the hole or seat 17 is omitted, the flange 23 rests on the contour of the wedge seat 16.
Finally, the sole comprises a reinforcement element 28 positioned below the insert 13 or in other positions of the sole where other inserts may be located, said reinforcement element 28 being formed, for example, of plastic material e.g. of natural or synthetic rubber and being advantageously somewhat transparent. Element 28 may or may not be tinted. Reinforcing element 28 is of a wear and abrasion resistant material and is preferably located in the heel portion and in the metatarsal portion of the sole.
During the use of an article of footwear according to this conventional insert, each time the user presses the lower part 1 of the article of footwear with his foot, the insert 13 is pressed towards the sole 2. Specifically, the pressing action exerted by the foot depresses the elements 14 which deform and increases the pressure within the airtight casing 15 which is constricted by the surrounding wall portion of its seat. When the user's heel ceases its pressing action, the elements 14 return to their initial configuration, so as to transmit a large part of the energy acquired during the pressing action to the user's foot, which therefore receives a gradual thrust at his heel (or other part of the foot, e.g., the metatarsal one) separates from the ground. To said thrust, exerted on the user's foot by elements 14, there must be added the thrust exerted by the air which is present inside insert 13, thus air being under pressure due to the action by the user's foot. These combined thrusts help transfer to the user's foot part of the energy transmitted by the user to the ground during movement.
Elastic inserts like the one disclosed above can be located in the other regions of the support part 1, in particular in proximity to the frontal region of the sole 2 and the wedge 3 and more particularly in the metatarsal zone 3A as shown in dotted lines in FIG. 179, where the seat is referenced by 16A and the insert by 13A, thus allowing the user (particularly an athlete) to obtain increased pickup during acceleration or during changes in the rate of movement.
The insert 13 shown in FIG. 179 and 181 comprises only one layer of elements 14; however, there can be provided an insert 13 having two or more layers of elements 14 superimposed as shown in FIG. 182. In particular, if the above cited insert has two layers of elements 14, a first layer supports the second whose deformable elements rest on the elements positioned below.
This conventional insert permits an improvement in the return of par of the energy (passed on by the user to the ground) to the foot of the user. It must be noted that, in the same manner previously described, free ends 18, 19 of barrel-shaped element 14, are fastened to (or soldered on) casing 15, whereas the contact surfaces of the two layers of element 14, if used, would be fastened to (or soldered on) each other. This affords stability for insert 13, preventing one of the layers from sliding over the other one within casing 15. An article of footwear constructed in accordance with the invention satisfies the aforesaid requirements and in particular enables most of the energy expended during movement to be retransferred to the foot.